Current planar radiating element and manifold technology using high dielectric constant materials cannot provide an integrated manifold and radiating element feed layer and good scan and polarization performance. Conventional probe fed patch apertures have gain and polarization limitations. Electronically scanned arrays often employ a circularly polarized field. Single linear polarization imposes inherent limitations on satellite communication. Dual polarization, with signals 90° out of phase, would be preferable if it could be achieved per-unit-cell.
Electronically scanned antennas generally comprise a manifold layer for distributing power to a feed layer. The feed layer feeds power to an aperture layer that couples the power to free space. The aperture layer typically requires low dielectric constant materials that are unsuitable for FR-4 manufacturing processes. Furthermore, existing aperture layers are substantially thicker than the manifold or feed layers, creating an unbalanced circuit board.
Probe fed apertures generally comprise a low dielectric constant substrate and two printed circuit board patches. Patches tend to scatter into lower order Floquet modes. Lower order Floquet modes must be relatively constant over the scan volume and frequency band, necessitating a small unit cell size and a low dielectric constant substrate. The small unit cell size results in a high module density, significantly increasing the cost of the antenna and the thermal loading problem. Furthermore, aperture performance as a function of frequency and scan is sub-optimal. Cross-polar coupling at wide H plane scan angles is also high because the probe is asymmetrical with respect to the H plane.
Probe coupled radiating elements combine the manifold and feed layers of a comparable aperture coupled radiating element resulting in a significant reduction in cost and manufacturing complexity. Current planar radiating element technology cannot provide a relatively broadband (˜30%) probe coupled dual polarized radiating element comprised exclusively of FR-4 materials, manufactured using standard printed circuit board (PCB) processes, and with a built in radome. Conventional probe coupled radiating elements require higher cost Teflon materials that are more expensive and difficult to manufacture than FR-4 materials. In addition, the unit cell size of a conventional probe coupled radiating element is small. Small unit cell size radiating elements are more expensive, and create module count, packaging, and heat dissipation problems.
Consequently, it would be advantageous if an apparatus existed that is efficient to manufacture and suitable for use as a radiating element having dual polarization in a single unit cell with moderately wide frequency bandwidth and scan volume, utilizing high dielectric constant materials.